(a) Field of the Invention
An aspect of the present invention relates to a display device, a driving device and a driving method thereof.
(b) Description of the Related Art
A liquid crystal display is one form of a flat panel display that is now widely used. Typically, the liquid crystal display includes two panels (e.g., upper and lower panels) in which field generating electrodes, such as pixel electrodes and common electrodes, are formed, with a liquid crystal layer interposed between the panels. During operation of the liquid crystal display, a voltage is applied to the field generating electrodes to generate an electric field in the liquid crystal layer, which determines the direction of liquid crystal molecules of the liquid crystal layer based on the generated electric field, and an image is displayed by controlling a polarization of incident light.
Among the various types of liquid crystal displays, a particular type of liquid crystal display operates in a vertically aligned (“VA”) mode. This type of liquid crystal display has a large contrast ratio and a wide reference viewing angle, in which long axes of liquid crystal molecules are aligned in a direction which is perpendicular to planes of the upper and lower panels when an electric field is not being applied. In this case, the reference viewing angle refers to a viewing angle at which a contrast ratio is either 1:10 or a luminance inversion limit angle between grays.
Achieving a wide viewing angle in a liquid crystal display operating in a VA mode includes forming a cutout in a field generating electrode, and forming a protrusion above or below the field generating electrode. Here, since the directions in which the liquid crystal molecules are inclined can be determined by the cutouts and the protrusions, the directions in which the liquid crystal molecules are inclined are dispersed in various directions using the cutouts and the protrusions to increase the reference viewing angle.
It has been seen, however, that the liquid crystal display operating in the VA mode has a problem in that side visibility is inferior to front visibility. For example, in the case of a liquid crystal display having cutouts which operates in a patterned vertically aligned (“PVA”) mode, an image becomes brighter one a viewer moves toward a side of the liquid crystal display so that there is no difference in luminance among high gray levels in a severe case and so that a picture generated by the liquid crystal display appears crumbled.
In order to account for this, individual pixels of the liquid crystal display are divided into two sub-pixels. The two sub-pixels are capacitively coupled with each other, and, therefore, an increased voltage is directly applied to one sub-pixel while a drop in voltage is caused in the other sub-pixel. Thus, the voltages of the two sub-pixels are made to be different from each other and, thus, the transmittances of the two sub-pixels are also made to be different from each other.
Due to the fact that the liquid crystal display of this example needs twice as many gate lines as compared with other liquid crystal displays, however, if the data voltages are applied with the general method, the pixels may not arrive at the object voltages due to associated short voltage charge times. As a result, polarity inversion becomes problematic. Accordingly, portions of the times that allow for the application of the gate-on voltages to the two neighboring gate lines need to be overlapped.
Here, it is noted that the timing of a gate signal applied to one sub-pixel and the timing of a gate signal applied to the other sub-pixel must be differently determined. However, since the portions of the times that allow for the application of the gate-on voltages to the two neighboring gate lines connected to each of the two sub-pixels need to be overlapped, the structure of the gate drivers is complicated.